vbox: allow specifying host only adapter cidr

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

docs/index.md

@@ -1464,6 +1464,7 @@ Options:
  - `--virtualbox-disk-size`: Size of disk for the host in MB.
  - `--virtualbox-boot2docker-url`: The URL of the boot2docker image. Defaults to the latest available version.
  - `--virtualbox-import-boot2docker-vm`: The name of a Boot2Docker VM to import.
+ - `--virtualbox-hostonly-cidr`: The CIDR of the host only adapter.
 
 The `--virtualbox-boot2docker-url` flag takes a few different forms.  By
 default, if no value is specified for this flag, Machine will check locally for
@@ -1482,6 +1483,15 @@ file://$HOME/Downloads/rc.iso` to test out a release candidate ISO that you have
 downloaded already.  You could also just get an ISO straight from the Internet
 using the `http://` form.
 
+To customize the host only adapter, you can use the `--virtualbox-hostonly-cidr`
+flag.  This will specify the host IP and Machine will calculate the VirtualBox
+DHCP server address (a random IP on the subnet between `.1` and `.25`) so 
+it does not clash with the specified host IP.
+Machine will also specify the DHCP lower bound to `.100` and the upper bound
+to `.254`.  For example, a specified CIDR of `192.168.24.1/24` would have a
+DHCP server between `192.168.24.2-25`, a lower bound of `192.168.24.100` and 
+upper bound of `192.168.24.254`.
+
 Environment variables and default values:
 
 | CLI option                           | Environment variable         | Default                  |
@@ -1491,6 +1501,7 @@ Environment variables and default values:
 | `--virtualbox-disk-size`             | `VIRTUALBOX_DISK_SIZE`       | `20000`                  |
 | `--virtualbox-boot2docker-url`       | `VIRTUALBOX_BOOT2DOCKER_URL` | *Latest boot2docker url* |
 | `--virtualbox-import-boot2docker-vm` | -                            | `boot2docker-vm`         |
+| `--virtualbox-hostonly-cidr`         | `VIRTUALBOX_HOSTONLY_CIDR`   | `192.168.99.1/24`        |
 
 #### VMware Fusion
 Creates machines locally on [VMware Fusion](http://www.vmware.com/products/fusion). Requires VMware Fusion to be installed.

drivers/virtualbox/virtualbox.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"math/rand"
 	"net"
 	"os"
 	"os/exec"
@@ -44,6 +45,7 @@ type Driver struct {
 	SwarmDiscovery      string
 	storePath           string
 	Boot2DockerImportVM string
+	HostOnlyCIDR        string
 }
 
 func init() {
@@ -86,6 +88,12 @@ func GetCreateFlags() []cli.Flag {
 			Usage: "The name of a Boot2Docker VM to import",
 			Value: "",
 		},
+		cli.StringFlag{
+			Name:   "virtualbox-hostonly-cidr",
+			Usage:  "Specify the Host Only CIDR",
+			Value:  "192.168.99.1/24",
+			EnvVar: "VIRTUALBOX_HOSTONLY_CIDR",
+		},
 	}
 }
 
@@ -150,6 +158,7 @@ func (d *Driver) SetConfigFromFlags(flags drivers.DriverOptions) error {
 	d.SwarmDiscovery = flags.String("swarm-discovery")
 	d.SSHUser = "docker"
 	d.Boot2DockerImportVM = flags.String("virtualbox-import-boot2docker-vm")
+	d.HostOnlyCIDR = flags.String("virtualbox-hostonly-cidr")
 
 	return nil
 }
@@ -273,7 +282,7 @@ func (d *Driver) Create() error {
 		return err
 	}
 
-	if err := setupHostOnlyNetwork(d.MachineName); err != nil {
+	if err := d.setupHostOnlyNetwork(d.MachineName); err != nil {
 		return err
 	}
 
@@ -360,7 +369,7 @@ func (d *Driver) Start() error {
 	}
 
 	// check network to re-create if needed
-	if err := setupHostOnlyNetwork(d.MachineName); err != nil {
+	if err := d.setupHostOnlyNetwork(d.MachineName); err != nil {
 		return err
 	}
 
@@ -564,6 +573,44 @@ func (d *Driver) generateDiskImage(size int) error {
 	return createDiskImage(d.diskPath(), size, raw)
 }
 
+func (d *Driver) setupHostOnlyNetwork(machineName string) error {
+	ip, network, err := net.ParseCIDR(d.HostOnlyCIDR)
+	nAddr := network.IP.To4()
+
+	var dhcpAddr net.IP
+	// select pseudo-random DHCP addr; make sure not to clash with the host
+	for {
+		n := rand.Intn(25)
+		if byte(n) != nAddr[3] {
+			dhcpAddr = net.IPv4(nAddr[0], nAddr[1], nAddr[2], byte(1))
+			log.Debugf("using %s for dhcp address", dhcpAddr)
+			break
+		}
+	}
+
+	hostOnlyNetwork, err := getOrCreateHostOnlyNetwork(
+		ip,
+		network.Mask,
+		dhcpAddr,
+		net.IPv4(nAddr[0], nAddr[1], nAddr[2], byte(100)),
+		net.IPv4(nAddr[0], nAddr[1], nAddr[2], byte(254)),
+	)
+
+	if err != nil {
+		return err
+	}
+
+	if err := vbm("modifyvm", machineName,
+		"--nic2", "hostonly",
+		"--nictype2", "82540EM",
+		"--hostonlyadapter2", hostOnlyNetwork.Name,
+		"--cableconnected2", "on"); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // createDiskImage makes a disk image at dest with the given size in MB. If r is
 // not nil, it will be read as a raw disk image to convert from.
 func createDiskImage(dest string, size int, r io.Reader) error {
@@ -670,27 +717,3 @@ func setPortForwarding(machine string, interfaceNum int, mapName, protocol strin
 	}
 	return actualHostPort, nil
 }
-
-func setupHostOnlyNetwork(machineName string) error {
-	hostOnlyNetwork, err := getOrCreateHostOnlyNetwork(
-		net.ParseIP("192.168.99.1"),
-		net.IPv4Mask(255, 255, 255, 0),
-		net.ParseIP("192.168.99.2"),
-		net.ParseIP("192.168.99.100"),
-		net.ParseIP("192.168.99.254"),
-	)
-
-	if err != nil {
-		return err
-	}
-
-	if err := vbm("modifyvm", machineName,
-		"--nic2", "hostonly",
-		"--nictype2", "82540EM",
-		"--hostonlyadapter2", hostOnlyNetwork.Name,
-		"--cableconnected2", "on"); err != nil {
-		return err
-	}
-
-	return nil
-}